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        <title>TDWG Ontology Design Guide</title>
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        <h1>TDWG Ontology Design Guide</h1>

        <p>These are design guidelines for the TDWG ontology. They explain how and where concepts
            should be specified so as to facilitate governance of the ontology in the long run.</p>

        <p>This is a practical document for people working on the ontology. <strong>This is not a
                TDWG standard or proposal.</strong></p>

        <h2>Components</h2>
        <ul>
            <li>
                <p>
                    <strong>Data</strong> This is the stuff that is produced and consumed over the
                    internet. Publishers express their data as RDF (or as a form that can be mapped
                    to RDF). The predicates and some of the objects in the RDF are resources defined
                    in the Vocabulary Files. i.e. the URIs used are to concepts (classes, properties
                    and individuals) defined in the vocabulary files. </p>
            </li>
            <li>
                <p>
                    <strong>Vocabulary Files</strong> These contain the definitions of the classes,
                    properties and individuals used in our domain. Each vocabulary file is a free
                    standing 'module' in that it does not reference anything defined in any other
                    vocabulary file. This is the primary mechanism to enable management of the
                    ontology.</p>
                <p> Consumers of data may resolve the URIs used in that data and import the
                    associated vocabulary files into their local analysis (or ontology). In doing so
                    they will acquire the basic meaning of the data. i.e. the definitions for the
                    resources they have data on. They will <strong>not</strong> import the whole of
                    the TDWG Ontology (including definitions of resources that are not in their
                    data) by doing this.</p>
                <p>Vocabulary Files are stored in the /ontologoy/voc/ directory.</p>
            </li>

            <li>
                <p>
                    <strong>Ontology Files</strong> Ontology files define how the classes and
                    properties in the vocabulary files are related. Each ontology file imports one
                    or more vocabulary files and makes assertions about how the contents of these
                    vocabulary files are related.</p>
                <p>Ontology files define nothing new - no classes, properties or individuals.</p>
                <p>As an example TaxonOntology.owl imports TaxonConcept.owl, TaxonName.owl and
                    TaxonRank.owl. It then asserts that TaxonConcept#hasName has the range
                    TaxonName#TaxonName and TaxonName#rank has the range TaxonRank#TaxonRank.
                    Although TaxonOntology.owl defines a uniform way of relating these three
                    vocabularies they are only loosely bound together and may be used in different
                    combinations in other ontologies. In the future ZooTaxonOntology.owl may defined
                    that places restrictions on interpretation of TaxonName.</p>
                <p>Consumers of data may choose to import ontology files into their analyses
                    separately from importing the data. They can be seen as an interpretation of the
                    vocabulary files.</p>
                <p>Ontology Files are stored in the /ontology/ directory.</p>
            </li>
        </ul>

        <p>The TDWG Ontology only defines things that are thought to be unique to the Biodiversity
            Informatics domain. Although the Ontology Files may bind the existing bricks in the
            Vocabulary Files to existing non-TDWG vocabularies there is should be no attempt to
            overload the meaning of external vocabularies or include references to these
            vocabularies in the Vocabulary Files.</p>

        <p>This approach to ontology construction can be described as a bricks and mortar approach.
            Vocabularies are independent bricks that are cemented together using the assertions in
            the ontology files but can be reassembled in different ways in the future should it be
            necessary.</p>

        <h2>OWL</h2>

        <p>The TDWG ontology is currently expressed in OWL. Wherever possible lowest common
            denominator OWL constructs should be used. Vocabulary Files should be OWL Lite. It is
            preferred Ontology Files are OWL Lite though OWL DL may be required.</p>


        <h2>Vocabulary Files Language Elements</h2>

        <p>The following language elements are permitted in vocabulary files</p>
        <ul>
            <li>owl:Class</li>
            <li>owl:ObjectProperty</li>
            <li>owl:DatatypeProperty</li>
            <li>rdfs:domain</li>
            <li>rdfs:range - only permitted when the object of the range is a class defined in the
                same file</li>
            <li>rdfs:label</li>
            <li>rdfs:comment</li>
            <li>rdfs:isDefinedBy</li>
        </ul>
        <p>The following language element are <strong>banned</strong> from vocabulary files</p>
        <ul>
            <li>owl:subClassOf</li>
            <li>rdfs:range - where the object of the range is a class not defined in the file</li>
        </ul>


        <h2>Ontology Files Language Elements</h2>

        <p>The following language elements are permitted in ontology files</p>
        <ul>
            <li>owl:subClassOf</li>
            <li>owl:range</li>
            <li>owl:domain</li>
        </ul>
        <p>The following language element are <strong>banned</strong> from ontology files</p>
        <ul>
            <li>owl:Class</li>
            <li>owl:ObjectProperty</li>
            <li>owl:DatatypeProperty</li>
        </ul>



        <h2>Relationship Between TDWG Ontology and TDWG Standards</h2>

        <p>There is not a one-to-one relationship between the files in the ontology and TDWG
            standards. Standards may cover particular property or class definitions and these may
            reside within files with the same </p>


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